diff options
Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.txt')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 288 |
1 files changed, 244 insertions, 44 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 26453f250683..86e2b586c171 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -113,7 +113,7 @@ the GPE dispatcher. This facility can be used to prevent such uncontrolled GPE floodings. - Format: <byte> + Format: <byte> or <bitmap-list> acpi_no_auto_serialize [HW,ACPI] Disable auto-serialization of AML methods @@ -225,14 +225,23 @@ For broken nForce2 BIOS resulting in XT-PIC timer. acpi_sleep= [HW,ACPI] Sleep options - Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, - old_ordering, nonvs, sci_force_enable, nobl } + Format: { s3_bios, s3_mode, s3_beep, s4_hwsig, + s4_nohwsig, old_ordering, nonvs, + sci_force_enable, nobl } See Documentation/power/video.rst for information on s3_bios and s3_mode. s3_beep is for debugging; it makes the PC's speaker beep as soon as the kernel's real-mode entry point is called. + s4_hwsig causes the kernel to check the ACPI hardware + signature during resume from hibernation, and gracefully + refuse to resume if it has changed. This complies with + the ACPI specification but not with reality, since + Windows does not do this and many laptops do change it + on docking. So the default behaviour is to allow resume + and simply warn when the signature changes, unless the + s4_hwsig option is enabled. s4_nohwsig prevents ACPI hardware signature from being - used during resume from hibernation. + used (or even warned about) during resume. old_ordering causes the ACPI 1.0 ordering of the _PTS control method, with respect to putting devices into low power states, to be enforced (the ACPI 2.0 ordering @@ -287,13 +296,21 @@ do not want to use tracing_snapshot_alloc() as it needs to be done where GFP_KERNEL allocations are allowed. + allow_mismatched_32bit_el0 [ARM64] + Allow execve() of 32-bit applications and setting of the + PER_LINUX32 personality on systems where only a strict + subset of the CPUs support 32-bit EL0. When this + parameter is present, the set of CPUs supporting 32-bit + EL0 is indicated by /sys/devices/system/cpu/aarch32_el0 + and hot-unplug operations may be restricted. + + See Documentation/arm64/asymmetric-32bit.rst for more + information. + amd_iommu= [HW,X86-64] Pass parameters to the AMD IOMMU driver in the system. Possible values are: - fullflush - enable flushing of IO/TLB entries when - they are unmapped. Otherwise they are - flushed before they will be reused, which - is a lot of faster + fullflush - Deprecated, equivalent to iommu.strict=1 off - do not initialize any AMD IOMMU found in the system force_isolation - Force device isolation for all @@ -301,6 +318,9 @@ allowed anymore to lift isolation requirements as needed. This option does not override iommu=pt + force_enable - Force enable the IOMMU on platforms known + to be buggy with IOMMU enabled. Use this + option with care. amd_iommu_dump= [HW,X86-64] Enable AMD IOMMU driver option to dump the ACPI table @@ -377,6 +397,9 @@ arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication support + arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension + support + ataflop= [HW,M68k] atarimouse= [HW,MOUSE] Atari Mouse @@ -497,16 +520,21 @@ ccw_timeout_log [S390] See Documentation/s390/common_io.rst for details. - cgroup_disable= [KNL] Disable a particular controller - Format: {name of the controller(s) to disable} + cgroup_disable= [KNL] Disable a particular controller or optional feature + Format: {name of the controller(s) or feature(s) to disable} The effects of cgroup_disable=foo are: - foo isn't auto-mounted if you mount all cgroups in a single hierarchy - foo isn't visible as an individually mountable subsystem + - if foo is an optional feature then the feature is + disabled and corresponding cgroup files are not + created {Currently only "memory" controller deal with this and cut the overhead, others just disable the usage. So only cgroup_disable=memory is actually worthy} + Specifying "pressure" disables per-cgroup pressure + stall information accounting feature cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1 Format: { { controller | "all" | "named" } @@ -581,6 +609,28 @@ loops can be debugged more effectively on production systems. + clocksource.max_cswd_read_retries= [KNL] + Number of clocksource_watchdog() retries due to + external delays before the clock will be marked + unstable. Defaults to three retries, that is, + four attempts to read the clock under test. + + clocksource.verify_n_cpus= [KNL] + Limit the number of CPUs checked for clocksources + marked with CLOCK_SOURCE_VERIFY_PERCPU that + are marked unstable due to excessive skew. + A negative value says to check all CPUs, while + zero says not to check any. Values larger than + nr_cpu_ids are silently truncated to nr_cpu_ids. + The actual CPUs are chosen randomly, with + no replacement if the same CPU is chosen twice. + + clocksource-wdtest.holdoff= [KNL] + Set the time in seconds that the clocksource + watchdog test waits before commencing its tests. + Defaults to zero when built as a module and to + 10 seconds when built into the kernel. + clearcpuid=BITNUM[,BITNUM...] [X86] Disable CPUID feature X for the kernel. See arch/x86/include/asm/cpufeatures.h for the valid bit @@ -674,6 +724,12 @@ hvc<n> Use the hypervisor console device <n>. This is for both Xen and PowerPC hypervisors. + { null | "" } + Use to disable console output, i.e., to have kernel + console messages discarded. + This must be the only console= parameter used on the + kernel command line. + If the device connected to the port is not a TTY but a braille device, prepend "brl," before the device type, for instance console=brl,ttyS0 @@ -800,11 +856,6 @@ Format: <port#>,<type> See also Documentation/input/devices/joystick-parport.rst - ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot - time. See - Documentation/admin-guide/dynamic-debug-howto.rst for - details. Deprecated, see dyndbg. - debug [KNL] Enable kernel debugging (events log level). debug_boot_weak_hash @@ -1092,6 +1143,11 @@ the driver will use only 32-bit accessors to read/write the device registers. + liteuart,<addr> + Start an early console on a litex serial port at the + specified address. The serial port must already be + setup and configured. Options are not yet supported. + meson,<addr> Start an early, polled-mode console on a meson serial port at the specified address. The serial port must @@ -1220,7 +1276,7 @@ The VGA and EFI output is eventually overwritten by the real console. - The xen output can only be used by Xen PV guests. + The xen option can only be used in Xen domains. The sclp output can only be used on s390. @@ -1541,8 +1597,10 @@ registers. Default set by CONFIG_HPET_MMAP_DEFAULT. hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation - of gigantic hugepages. - Format: nn[KMGTPE] + of gigantic hugepages. Or using node format, the size + of a CMA area per node can be specified. + Format: nn[KMGTPE] or (node format) + <node>:nn[KMGTPE][,<node>:nn[KMGTPE]] Reserve a CMA area of given size and allocate gigantic hugepages using the CMA allocator. If enabled, the @@ -1553,9 +1611,11 @@ the number of pages of hugepagesz to be allocated. If this is the first HugeTLB parameter on the command line, it specifies the number of pages to allocate for - the default huge page size. See also - Documentation/admin-guide/mm/hugetlbpage.rst. - Format: <integer> + the default huge page size. If using node format, the + number of pages to allocate per-node can be specified. + See also Documentation/admin-guide/mm/hugetlbpage.rst. + Format: <integer> or (node format) + <node>:<integer>[,<node>:<integer>] hugepagesz= [HW] The size of the HugeTLB pages. This is used in @@ -1567,6 +1627,23 @@ Documentation/admin-guide/mm/hugetlbpage.rst. Format: size[KMG] + hugetlb_free_vmemmap= + [KNL] Reguires CONFIG_HUGETLB_PAGE_FREE_VMEMMAP + enabled. + Allows heavy hugetlb users to free up some more + memory (6 * PAGE_SIZE for each 2MB hugetlb page). + Format: { on | off (default) } + + on: enable the feature + off: disable the feature + + Built with CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON=y, + the default is on. + + This is not compatible with memory_hotplug.memmap_on_memory. + If both parameters are enabled, hugetlb_free_vmemmap takes + precedence over memory_hotplug.memmap_on_memory. + hung_task_panic= [KNL] Should the hung task detector generate panics. Format: 0 | 1 @@ -1627,6 +1704,8 @@ architectures force reset to be always executed i8042.unlock [HW] Unlock (ignore) the keylock i8042.kbdreset [HW] Reset device connected to KBD port + i8042.probe_defer + [HW] Allow deferred probing upon i8042 probe errors i810= [HW,DRM] @@ -1695,6 +1774,11 @@ support for the idxd driver. By default it is set to true (1). + idxd.tc_override= [HW] + Format: <bool> + Allow override of default traffic class configuration + for the device. By default it is set to false (0). + ieee754= [MIPS] Select IEEE Std 754 conformance mode Format: { strict | legacy | 2008 | relaxed } Default: strict @@ -1892,18 +1976,17 @@ this case, gfx device will use physical address for DMA. strict [Default Off] - With this option on every unmap_single operation will - result in a hardware IOTLB flush operation as opposed - to batching them for performance. + Deprecated, equivalent to iommu.strict=1. sp_off [Default Off] By default, super page will be supported if Intel IOMMU has the capability. With this option, super page will not be supported. - sm_on [Default Off] - By default, scalable mode will be disabled even if the - hardware advertises that it has support for the scalable - mode translation. With this option set, scalable mode - will be used on hardware which claims to support it. + sm_on + Enable the Intel IOMMU scalable mode if the hardware + advertises that it has support for the scalable mode + translation. + sm_off + Disallow use of the Intel IOMMU scalable mode. tboot_noforce [Default Off] Do not force the Intel IOMMU enabled under tboot. By default, tboot will force Intel IOMMU on, which @@ -1987,7 +2070,7 @@ forcing Dual Address Cycle for PCI cards supporting greater than 32-bit addressing. - iommu.strict= [ARM64] Configure TLB invalidation behaviour + iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour Format: { "0" | "1" } 0 - Lazy mode. Request that DMA unmap operations use deferred @@ -1995,9 +2078,12 @@ throughput at the cost of reduced device isolation. Will fall back to strict mode if not supported by the relevant IOMMU driver. - 1 - Strict mode (default). + 1 - Strict mode. DMA unmap operations invalidate IOMMU hardware TLBs synchronously. + unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}. + Note: on x86, strict mode specified via one of the + legacy driver-specific options takes precedence. iommu.passthrough= [ARM64, X86] Configure DMA to bypass the IOMMU by default. @@ -2283,7 +2369,14 @@ [KVM] Controls how many 4KiB pages are periodically zapped back to huge pages. 0 disables the recovery, otherwise if the value is N KVM will zap 1/Nth of the 4KiB pages every - minute. The default is 60. + period (see below). The default is 60. + + kvm.nx_huge_pages_recovery_period_ms= + [KVM] Controls the time period at which KVM zaps 4KiB pages + back to huge pages. If the value is a non-zero N, KVM will + zap a portion (see ratio above) of the pages every N msecs. + If the value is 0 (the default), KVM will pick a period based + on the ratio, such that a page is zapped after 1 hour on average. kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. Default is 1 (enabled) @@ -2295,6 +2388,8 @@ kvm-arm.mode= [KVM,ARM] Select one of KVM/arm64's modes of operation. + none: Forcefully disable KVM. + nvhe: Standard nVHE-based mode, without support for protected guests. @@ -2302,7 +2397,9 @@ state is kept private from the host. Not valid if the kernel is running in EL2. - Defaults to VHE/nVHE based on hardware support. + Defaults to VHE/nVHE based on hardware support. Setting + mode to "protected" will disable kexec and hibernation + for the host. kvm-arm.vgic_v3_group0_trap= [KVM,ARM] Trap guest accesses to GICv3 group-0 @@ -2333,8 +2430,12 @@ Default is 1 (enabled) kvm-intel.emulate_invalid_guest_state= - [KVM,Intel] Enable emulation of invalid guest states - Default is 0 (disabled) + [KVM,Intel] Disable emulation of invalid guest state. + Ignored if kvm-intel.enable_unrestricted_guest=1, as + guest state is never invalid for unrestricted guests. + This param doesn't apply to nested guests (L2), as KVM + never emulates invalid L2 guest state. + Default is 1 (enabled) kvm-intel.flexpriority= [KVM,Intel] Disable FlexPriority feature (TPR shadow). @@ -2365,6 +2466,23 @@ feature (tagged TLBs) on capable Intel chips. Default is 1 (enabled) + l1d_flush= [X86,INTEL] + Control mitigation for L1D based snooping vulnerability. + + Certain CPUs are vulnerable to an exploit against CPU + internal buffers which can forward information to a + disclosure gadget under certain conditions. + + In vulnerable processors, the speculatively + forwarded data can be used in a cache side channel + attack, to access data to which the attacker does + not have direct access. + + This parameter controls the mitigation. The + options are: + + on - enable the interface for the mitigation + l1tf= [X86] Control mitigation of the L1TF vulnerability on affected CPUs @@ -2833,7 +2951,11 @@ Note that even when enabled, there are a few cases where the feature is not effective. - memtest= [KNL,X86,ARM,PPC,RISCV] Enable memtest + This is not compatible with hugetlb_free_vmemmap. If + both parameters are enabled, hugetlb_free_vmemmap takes + precedence over memory_hotplug.memmap_on_memory. + + memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest Format: <integer> default : 0 <disable> Specifies the number of memtest passes to be @@ -3152,6 +3274,19 @@ driver. A non-zero value sets the minimum interval in seconds between layoutstats transmissions. + nfsd.inter_copy_offload_enable = + [NFSv4.2] When set to 1, the server will support + server-to-server copies for which this server is + the destination of the copy. + + nfsd.nfsd4_ssc_umount_timeout = + [NFSv4.2] When used as the destination of a + server-to-server copy, knfsd temporarily mounts + the source server. It caches the mount in case + it will be needed again, and discards it if not + used for the number of milliseconds specified by + this parameter. + nfsd.nfs4_disable_idmapping= [NFSv4] When set to the default of '1', the NFSv4 server will return only numeric uids and gids to @@ -3159,6 +3294,7 @@ and gids from such clients. This is intended to ease migration from NFSv2/v3. + nmi_backtrace.backtrace_idle [KNL] Dump stacks even of idle CPUs in response to an NMI stack-backtrace request. @@ -3355,8 +3491,7 @@ difficult since unequal pointers can no longer be compared. However, if this command-line option is specified, then all normal pointers will have their true - value printed. Pointers printed via %pK may still be - hashed. This option should only be specified when + value printed. This option should only be specified when debugging the kernel. Please do not use on production kernels. @@ -3430,6 +3565,13 @@ shutdown the other cpus. Instead use the REBOOT_VECTOR irq. + nomodeset Disable kernel modesetting. DRM drivers will not perform + display-mode changes or accelerated rendering. Only the + system framebuffer will be available for use if this was + set-up by the firmware or boot loader. + + Useful as fallback, or for testing and debugging. + nomodule Disable module load nopat [X86] Disable PAT (page attribute table extension of @@ -3569,6 +3711,12 @@ off: turn off poisoning (default) on: turn on poisoning + page_reporting.page_reporting_order= + [KNL] Minimal page reporting order + Format: <integer> + Adjust the minimal page reporting order. The page + reporting is disabled when it exceeds (MAX_ORDER-1). + panic= [KNL] Kernel behaviour on panic: delay <timeout> timeout > 0: seconds before rebooting timeout = 0: wait forever @@ -4101,6 +4249,15 @@ Format: <bool> (1/Y/y=enable, 0/N/n=disable) default: disabled + printk.console_no_auto_verbose= + Disable console loglevel raise on oops, panic + or lockdep-detected issues (only if lock debug is on). + With an exception to setups with low baudrate on + serial console, keeping this 0 is a good choice + in order to provide more debug information. + Format: <bool> + default: 0 (auto_verbose is enabled) + printk.devkmsg={on,off,ratelimit} Control writing to /dev/kmsg. on - unlimited logging to /dev/kmsg from userspace @@ -4293,6 +4450,11 @@ whole algorithm to behave better in low memory condition. + rcutree.rcu_delay_page_cache_fill_msec= [KNL] + Set the page-cache refill delay (in milliseconds) + in response to low-memory conditions. The range + of permitted values is in the range 0:100000. + rcutree.jiffies_till_first_fqs= [KNL] Set delay from grace-period initialization to first attempt to force quiescent states. @@ -4706,7 +4868,7 @@ reboot= [KNL] Format (x86 or x86_64): - [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \ + [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \ [[,]s[mp]#### \ [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ [[,]f[orce] @@ -4871,11 +5033,21 @@ an IOTLB flush. Default is lazy flushing before reuse, which is faster. + s390_iommu_aperture= [KNL,S390] + Specifies the size of the per device DMA address space + accessible through the DMA and IOMMU APIs as a decimal + factor of the size of main memory. + The default is 1 meaning that one can concurrently use + as many DMA addresses as physical memory is installed, + if supported by hardware, and thus map all of memory + once. With a value of 2 one can map all of memory twice + and so on. As a special case a factor of 0 imposes no + restrictions other than those given by hardware at the + cost of significant additional memory use for tables. + sa1100ir [NET] See drivers/net/irda/sa1100_ir.c. - sbni= [NET] Granch SBNI12 leased line adapter - sched_verbose [KNL] Enables verbose scheduler debug messages. schedstats= [KNL,X86] Enable or disable scheduled statistics. @@ -5194,8 +5366,7 @@ auto - Kernel selects the mitigation depending on the available CPU features and vulnerability. - Default mitigation: - If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl" + Default mitigation: "prctl" Not specifying this option is equivalent to spectre_v2_user=auto. @@ -5239,7 +5410,7 @@ will disable SSB unless they explicitly opt out. Default mitigations: - X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl" + X86: "prctl" On powerpc the options are: @@ -5388,6 +5559,15 @@ stifb= [HW] Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] + strict_sas_size= + [X86] + Format: <bool> + Enable or disable strict sigaltstack size checks + against the required signal frame size which + depends on the supported FPU features. This can + be used to filter out binaries which have + not yet been made aware of AT_MINSIGSTKSZ. + sunrpc.min_resvport= sunrpc.max_resvport= [NFS,SUNRPC] @@ -5611,12 +5791,25 @@ Note, echoing 1 into this file without the tracepoint_printk kernel cmdline option has no effect. + The tp_printk_stop_on_boot (see below) can also be used + to stop the printing of events to console at + late_initcall_sync. + ** CAUTION ** Having tracepoints sent to printk() and activating high frequency tracepoints such as irq or sched, can cause the system to live lock. + tp_printk_stop_on_boot[FTRACE] + When tp_printk (above) is set, it can cause a lot of noise + on the console. It may be useful to only include the + printing of events during boot up, as user space may + make the system inoperable. + + This command line option will stop the printing of events + to console at the late_initcall_sync() time frame. + traceoff_on_warning [FTRACE] enable this option to disable tracing when a warning is hit. This turns off "tracing_on". Tracing can @@ -6227,6 +6420,13 @@ improve timer resolution at the expense of processing more timer interrupts. + xen.balloon_boot_timeout= [XEN] + The time (in seconds) to wait before giving up to boot + in case initial ballooning fails to free enough memory. + Applies only when running as HVM or PVH guest and + started with less memory configured than allowed at + max. Default is 180. + xen.event_eoi_delay= [XEN] How long to delay EOI handling in case of event storms (jiffies). Default is 10. |